Synchronize RGB Hex values from official Nord palette

Align the ANSI and other iTerm2 colors to the Nord color palette.

The following values have changed in the iTerm2 Settings > Profiles >
Colors panel, noting changes in colors:

Basic Colors
------------
- Foreground    (nord4): #d8dde8 -> #d8dee9
- Background    (nord0): #2e333f -> #2e3440
- Bold          (nord6): #eceef3 -> #eceff4
- Links         (nord5): #e5e8ef -> #e5e9f0
- Selection     (nord2): #4c5569 -> #434c5e
                         (nord3) -> (nord2)
- Selected text (nord4): #d8dde8 -> #d8dee9
- Tab color     (nord1): #3b4151 -> #3b4252

Cursor Colors
-------------
- Cursor       (nord4): #d8dde8 -> #d8dee9
- Cursor text  (nord1): #3b4151 -> #3b4252
- Cursor guide (nord2): #3b4151 -> #434c5e
                        (nord1)    (nord2)

ANSI Colors
-----------
- Normal Black     (nord1): #3b4151  -> #3b4252
- Bright Black     (nord3): #4c5569  -> #4c566a
- Normal Red      (nord11): #be6069  -> #bf616a
- Bright Red      (nord11): #be6069  -> #bf616a
- Normal Green    (nord14): #a3bd8b  -> #a3be8c
- Bright Green:   (nord14): #a3bd8b  -> #a3be8c
- Normal Yellow:  (nord13): #ebca8a  -> #ebcb8b
- Bright Yellow:  (nord12): #ebca8a  -> #d08770
                            (nord13)    (nord12)
- Normal Blue:     (nord9): #81a0c0  -> #81a1c1
- Bright Blue:    (nord10): #81a0c0  -> #5e81ac
                            (nord9)     (nord10)
- Normal Magenta: (nord15): #b48dac  -> #b48ead
- Bright Magenta: (nord15): #b48dac  -> #b48ead
- Normal Cyan:     (nord8): #88bfcf  -> #88c0d0
- Bright Cyan:     (nord7): #8fbbba  -> #8fbcbb
- Normal White:    (nord5): #e5e8ef  -> #e5e9f0
- Bright White:    (nord6): #eceef3  -> #eceff4

The text selection and cursor guide uses nord2 now to align with
"currently active text editor line as well as selection."

Bright Blue uses nord10, the next accent level, for tertiary UI
elements. Using nord12 may be a stretch for Bright Yellow. With both
these changes, all of Frost and Aurora are available.